Animals use their olfactory sensory systems to interact with the complex and heterogeneous environment. Although we have discovered much about how olfactory systems work, we still do not well understand how an odor is translated into information in the brain. The Drosophila larva is an ideal system in which to test hypotheses about odor coding. Larvae have few olfactory receptor neurons, yet display sophisticated olfactory mediated behaviors. I propose an examination of olfactory receptors in Drosophila larvae using genetic, behavioral, and physiological analysis. I will test the hypothesis that Odorant receptor (Or) genes act as olfactory receptors in the larva. Furthermore, I plan to test the contribution of Or genes to olfactory behavior in the larvae. [unreadable] [unreadable]